加快MySQL加入检查重复 [英] Speed up MySQL join to check for duplicates

问题描述

我使用以下查询返回所有具有相同名称和重要名称的重复记录。诀窍是，contact_id必须是降序。

I'm using the following query to return all duplicate records with the same first and last name. The trick is that the contact_id, has to be in descending order.

查询按预期返回联系人，但它只是SO SLOW！在检查大约30,000条记录的时候，大约需要6-8秒。

The query returns the contacts as expected, but it is just SO SLOW! Takes about 6-8 seconds when checking around 30,000 records.

我有contact_firstName，contact_lastName，contact_client_id和contact_id都在数据库中索引。

I have the contact_firstName, contact_lastName, contact_client_id, and contact_id all indexed in the database.

任何想法我可以做些什么来尝试加速一点？感谢您的帮助：）

Any ideas what I could do to try and speed this up a bit? Thanks for your help :)

SELECT z.contact_id, z.contact_firstName, z.contact_lastName, RIGHT(z.contact_lastName,1) AS nameNum
FROM (`contacts` x) 
JOIN `contacts` z ON `x`.`contact_firstName` = `z`.`contact_firstName` 
AND x.contact_lastName = z.contact_lastName 
AND x.contact_client_id = ".$ID." 
AND z.contact_client_id = ".$ID." 
WHERE `x`.`contact_id` < `z`.`contact_id` 
GROUP BY `z`.`contact_id` 

推荐答案

不作任何承诺，但这是替代尝试：

Not making any promises, but here's an alternative to try:

SELECT c.contact_id, c.contact_firstName, c.contact_lastName, RIGHT(c.contact_lastName,1) AS nameNum
    FROM (SELECT contact_firstName, contact_lastName, MIN(contact_id) AS MinID
              FROM contacts
              WHERE contact_client_id = ".$ID."
              GROUP BY contact_firstName, contact_lastName
              HAVING COUNT(*) > 1) t
        INNER JOIN contacts c
            ON t.contact_firstName = c.contact_firstName
                AND t.contact_lastName = c.contact_lastName
                AND c.contact_client_id = ".$ID."
                AND t.MinID <> c.contact_id

这篇关于加快MySQL加入检查重复的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！